Testing Sonoma Ash and Air for Fire-Formed Pollutants

The Northern California wildfires of 2017 may have created new kinds of pollutants by incinerating housing materials and household items. UC Davis researchers will study samples of ash and air from sites such as this house in Larkfield-Wikiup and plan to survey residents on their experiences. (Photo by Gabrielle Black)

When fires ripped through suburban subdivisions in Santa Rosa last October, they may have done more than reduce homes to ashes. By incinerating all kinds of materials — insulation, electronics, furniture, cleaning products, pesticides — at very high temperatures, they could have created unknown or previously unrecognized health hazards in the smoke and ash. Researchers from the University of California, Davis, are trying to figure out just what is in that ash and air.

“What we’re interested in looking for are transformation products of household products that have burned in the fires,” said Gabby Black, a fourth-year graduate student in agricultural and environmental chemistry at UC Davis.

According to Tom Young, professor in the Department of Civil and Environmental Engineering and Black’s faculty advisor, the health hazards these compounds pose are not yet known.

“Conventional assessments rely on things that we already know are pollutants, such as industrial chemicals,” Young said. “But we don’t know what new chemicals might have been created from combustion.”

The Northern California Fire and Health Impacts project, also known as “Wildfires and Health: Assessing the Toll in NOrthWest California” (WHAT NOW-California) is led by Irva Hertz-Picciotto, professor of public health sciences and director of the UC Davis Environmental Health Sciences Center. In addition to sampling ash and air, researchers from the center plan to survey residents of Napa, Sonoma and other Northern California counties affected by the fires or the smoke. The wildfire survey asks about how the fires have affected them and other household members, including their experiences as well as their health before, during and after the fires.

Black, who was born and raised in Sonoma, has collected ash samples from a series of sites burned by the Tubbs Fire in October, from wildland in Robert Louis Stevenson State Park into the city of Santa Rosa.

In addition, researcher Keith Bein and colleagues from the UC Davis Air Quality Research Center plan to regularly collect air samples from these sites as the area recovers from the fires. While the fires were still burning, Bein’s team collected samples of smoky air in the Bay Area and Davis. But for years to come, they expect, dust in the burned area will contain particles of fire ash. The researchers will look specifically at airborne particles less than 2.5 microns in size that can penetrate deep into the lungs.

Air and ash samples will be analyzed by the latest techniques that can generate high-resolution profiles of hundreds or thousands of molecules in a sample. The researchers will compare the samples to existing databases and also look for new compounds.

“This was a very unique type of fire, an urban wildfire,” Bein said. “We know what wildfire smoke is composed of, but we have no idea what will be in this — we expect it to be very different.”

The air quality team has set up a mobile air sampling unit powered by an electric vehicle. The system can carry out 24 hours of continuous sampling in a remote area with no accessible power. They plan to begin monthly sampling in the Sonoma and Napa areas this spring. In future, Bein hopes that the mobile unit can be deployed quickly into an affected area.

The project has received initial funding from the UC Davis Environmental Health Science Center, sponsored by the National Institute for Environmental Health Sciences. Black is supported by an NSF graduate student fellowship.